Identification of the embryonic stage when injury can cause autism has led to the insight that the disorder is initiated by changes in the developing brain stem. We propose that teratogens and genetic defects lead to similar developmental changes in the brain stem because mutations of early developmental genes are the cause of familial cases and the teratogens which cause the disease act by interfering with the function of the same genes. This project will continue to identify genetic causes of autism based on data about the developmental origin and neuroanatomical phenotype responsible for some cases of the disease.